The danger of polychlorinated biphenyls (PCB's) is well documented. They were used in insulating fluids for processing equipment until banned in 1979. Believed to cause cancer, liver and skin damage, sterility and brain damage, the compound has a surprising longevity and once within a human's body, does not dissipate and builds a significant body burden as a function of frequency and level of exposure.
Utility companies introduced PCB's in gas line networks to clean out particulates such as rust, dust, moisture or other gas-laden impurities. Gas line compressor stations also used PCB contaminated oil until banned by Congress. While the EPA and various State Agencies are aware of the problem of PCB's in gas lines, they do not think the exposure danger is of sufficient levels, do not monitor PCB's concentration adjacent to a customer's home, business or like and moreover, do not know how to expunge PCB's from the gas line network since the PCB-contained oil is scrub resistent.
In such situation, I find that surprisingly large PCB concentrations sporadically occur. Sources of such concentration: dampening effects of the compressor-driven network, multiple customer outlet usage, and maintenance practices that add to aperiodic loading of the natural gas stream coupled with surprising longevity of the in situ PCB's. As a result, PCB's can flow to appliances in the customer's home, business or the like at sufficient levels to be a health hazard, exceed "Federal and/or State health and safety standards. Moreover, since the original source of the PCB's is in the liquid phase, both gas phase and liquid phases (say attached in aerosol form to gas born particulates) are combinable and form the final end-use contamination levels at the appliance to be used.